“The Essex Amphibious Ready Group with embarked 13th Marine Expeditionary Unit got underway from San Diego, Tuesday,” Pacific Fleet spokesman Capt. Charlie Brown said in a statement to USNI News. “For reasons of operational security, we are not publicly disclosing any additional details.”

Typically the departures are announced days in advance so that families and the media can attend.

The ready group carries 5,000 sailors and Marines, including the “Wake Island Avengers” of Marine Fighter Attack Squadron (VMFA) 211 flying the new F-35B stealth fighter. The Essex is carrying the jets for the first time, along with its complement of helicopters and tiltrotors.